CVE-2026-64394 (GCVE-0-2026-64394)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:50 – Updated: 2026-07-27 05:00
VLAI
Title
ksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2 SET_INFO SECURITY
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2 SET_INFO SECURITY commit cc57232cae23 ("ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE") added a fp->daccess gate to fsctl_set_sparse and noted that "similar handle-level checks exist in other functions but are missing here." The SMB2 SET_INFO SECURITY arm is one of the missing ones, and the most security-relevant: smb2_set_info_sec() calls set_info_sec() with no per-handle access check. set_info_sec() (fs/smb/server/smbacl.c) re-permissions the file: it rewrites owner/group/mode via notify_change(), rewrites the POSIX ACL via set_posix_acl(), and on KSMBD_SHARE_FLAG_ACL_XATTR shares removes and rewrites the Windows security descriptor via ksmbd_vfs_set_sd_xattr(). Every other persistent-mutation arm of the sibling handler smb2_set_info_file() checks fp->daccess first (FILE_WRITE_DATA / FILE_DELETE / FILE_WRITE_EA / FILE_WRITE_ATTRIBUTES); the SECURITY arm — which mutates the access control itself — is the only one with no gate. A client can therefore open a handle with FILE_WRITE_ATTRIBUTES only (no FILE_WRITE_DAC / FILE_WRITE_OWNER) and use SMB2_SET_INFO with InfoType SMB2_O_INFO_SECURITY to rewrite the file's DACL and owner, granting itself access the handle's daccess never carried. Unlike the FSCTL data arms this is a metadata/xattr operation, so there is no FMODE_WRITE VFS backstop — the missing fp->daccess check is the entire gate. Setting a security descriptor is the WRITE_DAC / WRITE_OWNER operation, so require at least one of those on the handle before re-permissioning the file. -EACCES is mapped to STATUS_ACCESS_DENIED by smb2_set_info().
Severity
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 0848b1d8b403f530878195dcbe241a2fddb9d0e1 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < e6aa731f1b4b3e08caebf66a99f04b22bdab2e99 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 9ab2ffd3ed3d4ca1667c52de27026ddabc11e537 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < f56535db508ead8dec1c481ad93d7d8acd8f8f1e (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < aae600cdaffc6d9ce97645f129799a103a97d06d (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 44df157a1183a7f746caa970c169255da5ac61f8 (git)
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Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.96 , ≤ 6.12.* (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 7.1.4 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix)
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    "dateReserved": "2026-07-19T15:36:31.785Z",
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Unlike the FSCTL data arms this\\nis a metadata/xattr operation, so there is no FMODE_WRITE VFS backstop \u2014\\nthe missing fp-\u003edaccess check is the entire gate.\\n\\nSetting a security descriptor is the WRITE_DAC / WRITE_OWNER operation, so\\nrequire at least one of those on the handle before re-permissioning the\\nfile. -EACCES is mapped to STATUS_ACCESS_DENIED by smb2_set_info().\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/smb/server/smb2pdu.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"0848b1d8b403f530878195dcbe241a2fddb9d0e1\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"e6aa731f1b4b3e08caebf66a99f04b22bdab2e99\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"9ab2ffd3ed3d4ca1667c52de27026ddabc11e537\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"f56535db508ead8dec1c481ad93d7d8acd8f8f1e\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"aae600cdaffc6d9ce97645f129799a103a97d06d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"44df157a1183a7f746caa970c169255da5ac61f8\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/smb/server/smb2pdu.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.15\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.15\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.178\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.145\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.96\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.39\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.4\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2-rc1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":8.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0848b1d8b403f530878195dcbe241a2fddb9d0e1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/44df157a1183a7f746caa970c169255da5ac61f8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9ab2ffd3ed3d4ca1667c52de27026ddabc11e537\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/aae600cdaffc6d9ce97645f129799a103a97d06d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/e6aa731f1b4b3e08caebf66a99f04b22bdab2e99\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f56535db508ead8dec1c481ad93d7d8acd8f8f1e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "suse_vex": {
      "aggregate_severity": "not set",
      "current_release_date": "2026-07-25T16:00:10Z",
      "cve": "CVE-2026-64394",
      "id": "CVE-2026-64394",
      "initial_release_date": "2026-07-25T16:00:10Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64394",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64394.json",
      "version": "2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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